Aimed at the potential overload problems caused by the uncertainty of the arrived data in a data stream management system, the load shedding issue of the data stream system is researched. Focus on the condition that exists join operators of two streams, a semantic-based load shedding technique is applied. A data stream load shedding model is designed and implemented, which solves four problems including load shedding and anti-shedding time, amount, location and selecting predicate. The experiment result is analyzed, which shows that the load shedding model presented can effectively avoid the low processing efficiency when system is overload, and guarantee the coordination of arrived data and system processing capability, and make a combination of system stability and correctness as a result.